3 Character reconstructions

This page provides definitions for each of the characters in our matrix, and justifies codings in particular taxa where relevant. Further citations for codings that are not discussed in the text can be viewed by browsing the morphological dataset on MorphoBank (project 2800). This link will become live on publication of the paper. Referees should follow the pre-publication link to the dataset that has been provided in the main manuscript.

Alongside each character’s definition, each character is mapped onto a tree. The tree used for reconstruction can be selected using the links below. Each tip is labelled as it is coded in the matrix, and these states are used to reconstruct the condition of each internal node, using the parsimony method of Brazeau et al. (2018) as implemented in the Inapp R package.

We emphasize that different trees will give different reconstructions. The character mappings are not intended to definitively establish how each character evolved, but to help the reader quickly establish how each character has been coded, and to visualize at a glance how well the character fits onto the given tree. We consider this more intuitive than the use of the flawed (Archie, 1989) Consistency Index, but include this value because of its historic significance.

3.1 Sclerites

[1] Present in adult

Select tree:

Character 1: Sclerites: Present in adult

0: Absent
1: Present
Neomorphic character.

Plate-like (wider than tall) skeletal elements, whether mineralized or non-mineralized.
The definition deliberately excludes setae (which are taller than wide).

3.2 Sclerites: Bivalved [2]

Select tree:

Character 2: Sclerites: Bivalved

0: Scleritomous: without differentiated dorsal and ventral valves
1: Bivalved: scleritome dominated by prominent dorsal and ventral valve
Neomorphic character.

Scleritome dominated by prominent differentiated dorsal and ventral valves.

[3] Accessory sclerites reduced

Select tree:

Character 3: Sclerites: Bivalved: Accessory sclerites reduced

0: Accessory sclerites present
1: Accessory sclerites absent: two valves only
Neomorphic character.

Taxa in the bivalved condition may retain sclerites as small additional elements, such as the L-elements of Paterimitra (Skovsted et al., 2015).

This character is treated as neomorphic, with accessory sclerites ancestrally present, recognizing the likely origin of brachiozoans (and Lophotrochozoans more generally) from a scleritomous organism.

Coded as inapplicable in taxa that lack multiple skeletal elements.

Haplophrentis carinatus: Coded as ambiguous to recognize the possibility that helens may correspond to L-elements of Paterimitra (Moysiuk, Smith, & Caron, 2017).

Paterimitra: L-sclerites (Skovsted et al., 2009).

[4] Hinge line shape

Select tree:

Character 4: Sclerites: Bivalved: Hinge line shape

1: Astrophic
2: Strophic
Transformational character.

Botsfordia: Coded as dissociated in Williams et al. (1998), appendix 2.

Craniops: Astrophic: rounded posterior margin (see fig. 91 in Williams et al., 2000).

Gasconsia: The straight posterior margin of Gasconsia contributes to an overall resemblance with the Chileids (???).

Kutorgina chengjiangensis: Williams et al. (2000, p. 208) consider the hinge of Kutorgina to be stropic, whereas Bassett et al. (2001) argue for an astropic interpretation – whilst noting that the arrangement is prominently different from other astrophic taxa. We therefore code this taxon as ambiguous.

Longtancunella chengjiangensis: “Longtancunella has an oval to subcircular shell with a very short strophic hinge line” – Z.-F. Zhang, Holmer, Ou, Han, & Shu (2011).

Mickwitzia muralensis: non-strophic.

Micrina: See Holmer, Skovsted, Brock, Valentine, & Paterson (2008).

Nisusia sulcata: “The strophic, articulated shells of the Kutorginata rotated on simple hinge mechanisms that are different from those of other rhynchonelliforms” (Williams et al., 2000, p. 208).

Novocrania: Craniides have a strophic posterior valve edge (Williams et al., 2007, table 39 on p. 2853): Novocrania’s “dorsal posterior margin” is “straight” (Williams et al., 2000, p. 171).

Tomteluva perturbata: “Tomteluvid taxa all have a strongly ventribiconvex, astrophic shell with a unisulcate commissure” – Streng, Butler, Peel, Garwood, & Caron (2016), p5.

Yuganotheca elegans: Not evident from fossil material; the possibility of a short strophic hinge line (as in Longtancunella) is difficult to discount.

References

Brazeau, M. D., Guillerme, T., & Smith, M. R. (2018). An algorithm for morphological phylogenetic analysis with inapplicable data. Systematic Biology. doi:10.1101/209775

Archie, J. W. (1989). Homoplasy excess ratios: new indices for measuring levels of homoplasy in phylogenetic systematics and a critique of the Consistency Index. Systematic Zoology, 38(3), 253. doi:10.2307/2992286

Skovsted, C. B., Betts, M. J., Topper, T. P., & Brock, G. A. (2015). The early Cambrian tommotiid genus Dailyatia from South Australia. Memoirs of the Association of Australasian Palaeontologists, 48(1), 1–117.

Moysiuk, J., Smith, M. R., & Caron, J.-B. (2017). Hyoliths are Palaeozoic lophophorates. Nature, 541(7637), 394–397. doi:10.1038/nature20804

Skovsted, C. B., Holmer, L. E., Larsson, C. M., Högström, A. E. S., Brock, G. A., Topper, T. P., … Paterson, J. R. (2009). The scleritome of Paterimitra: an Early Cambrian stem group brachiopod from South Australia. Proceedings of the Royal Society B: Biological Sciences, 276, 1651–1656. doi:10.1098/rspb.2008.1655

Williams, A., Popov, L. E., Holmer, L. E., & Cusack, M. (1998). The diversity and phylogeny of the paterinate brachiopods. Palaeontology, 41, 221–262.

Williams, A., Carlson, S. J., Brunton, C. H. C., Holmer, L. E., Popov, L. E., Mergl, M., … Wright, A. D. (2000). Linguliformea, Craniiformea, and Rhynchonelliformea (part). In Treatise on invertebrate paleontology, part h, brachiopoda (revised) (Vol. 2 & 3, pp. 1–919). Geological Society of America & Paleontological Institute. doi:10.17161/dt.v0i0.5215

Bassett, M. G., Popov, L. E., & Holmer, L. E. (2001). Functional morphology of articulatory structures and implications for patterns of musculature in Cambrian rhynchonelliform brachiopods. In H. Brunton, R. M. Cocks, & S. L. Long (Eds.), Brachiopods, past and present (pp. 163–176). Taylor & Francis. doi:10.1201/9780203210437.pt3

Zhang, Z.-F., Holmer, L. E., Ou, Q., Han, J., & Shu, D.-G. (2011). The exceptionally preserved Early Cambrian stem rhynchonelliform brachiopod Longtancunella and its implications. Lethaia, 44(4), 490–495. doi:10.1111/j.1502-3931.2011.00261.x

Holmer, L. E., Skovsted, C. B., Brock, G. A., Valentine, J. L., & Paterson, J. R. (2008). The Early Cambrian tommotiid Micrina, a sessile bivalved stem group brachiopod. Biology Letters, 4, 724–728. doi:10.1098/rsbl.2008.0277

Williams, A., Racheboeuf, P. R., Savage, N. M., Lee, D. E., Popov, L. E., Carlson, S. J., … Jia-Yu, J.-R. (2007). Supplement. In Treatise on invertebrate paleontology, part h, brachiopoda (revised) (Vol. 6, pp. 2321–3226). Geological Society of America & Paleontological Institute. doi:10.17161/dt.v0i0.5526

Streng, M., Butler, A. D., Peel, J. S., Garwood, R. J., & Caron, J.-B. (2016). A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology. Palaeontology, 59(2), 269–293. doi:10.1111/pala.12226